EFFECT OF SEEDING DATE, RATE AND DEPTH ON WINTER-WHEAT GROWN ON CONVENTIONAL FALLOW IN SW SASKATCHEWAN

Winter wheat (Triticum aestivum L.) seeded on conventional fallow is considered to have a high risk of winterkill in the Brown soil zone of the Canadian Prairies, yet many producers in this area continue to use this approach. Although this system is subject to frequent winterkill, the alternative (seeding into standing stubble) is itself subject to frequent economic loss due to drought stress. A 4-yr study was carried out on a medium-textured, Orthic Brown Chernozem using Norstar winter wheat seeded into bare fallow land. Several seeding dates, depths and rates were tested to determine if alternate management strategies could be used to enhance the chances of overwinter survival thereby improving the incidence of successful production when this crop was grown on conventional fallow. Multiple regression was used to relate grain yields and plant counts (survival over winter) to the number of days before freeze-up when the crop was seeded and the other treatment factors. Results confirmed those reported in southern Alberta. For example, production was very variable and both plant survival and grain yields were mainly influenced by seeding date, with the optimum seeding period being the first 2 wk of September; yields decreased sharply on both sides of this period. However, seeding just prior to freeze-up gave higher yields than seeding 2 or 3 wk prior to freeze-up even though this latest seeded material did not germinate until spring. Depth of seeding influenced plant survival but had little influence on yield. The 5.0-cm depth was recommended as the best for fallow. Seeding rate influenced plant survival and yields more so than depth, but the influence was not large and none of the three treatments prevented severe winterkill when temperatures were extremely low. We recommended that a seeding rate of 60 kg ha-1 be chosen for fallow as is the case for stubble seeded wheat. Grain protein was not influenced by any treatment and was mainly a function of moisture deficit (year). In spite of the variability in production with this system of management, producers may still choose to grow winter wheat on conventional fallow since if winterkilling occurs they have the option of reseeding the area to spring wheat.